The subject invention may be incorporated in various types of fluid operated rotary power tools having a variety of different applications. A typical application is the use of the torque control clutch of this invention in an air operated screwdriver, e.g., in bench assembly of electric and electronic gear. Such tools must be highly reliable over hundereds of thousands of cycles in addition of being durable and readily adjustable to deliver a predetermined torque applied to a fastener by the tool during its operation.
Known fastener setting power tools frequently utilize clutch mechanisms in the tools, such as screwdrivers, many of which mechanisms are spring and cam arrangements. Under torque load, a cam between the driving and driven clutch parts, with or without rollers, is utilized to move the clutch members in an axial direction against an adjustable spring force. Such clutch members disengage and re-engage, sometimes providing an impacting effect. Other such tools utilize latch and push rod arrangements for shutting off the tool.
The disadvantages of such known devices include kinetic inertial effects in the disengaging members, such as a clutch part being accelerated axially by a cam against a spring, and these inertial effects are undesirably reflected in the output torque applied by the tool. Simply stated, most such clutches provide a dynamic output torque higher than their static disengaging torque. In addition, certain known tools, while reliable and providing accurate clutch action, are unduly structurally complex and present difficulties and time consuming efforts to service the tools.